1. Field of the Invention
The present invention relates to a process and device for forming hollow glass objects, as well as the objects obtained. In particular, it deals with the production of objects such as bottles exhibiting a neck which may be threaded, where the production uses the so-called "blown-blown" technique.
2. Description of the Related Art
This technique, well known to those skilled in the art, can be schematically subdivided into three phases: the initial phase, the transfer phase, and the finishing phase.
The initial phase is the phase of forming the blank starting with a glass gob under compression in a parison mold and using a mechanical operation to initially puncture the neck, and then having an actual piercing operation performed by blowing into the blank.
The transfer phase consists of swinging the blank into the finishing mold while holding it by the neck.
The finishing phase is the one where the blank acquires its final shape in the finishing mold due to a second blowing operation.
Thus, in this technique the internal profile of the bottles is molded by pneumatic forces which are exerted against the internal walls of the bottle being formed, and this happens both during the initial phase and during the finishing phase, this in contrast to the so-called "pressed-blown" technique, in which during the initial phase the blank is pressed mechanically by a counter mold called a punch.
This means that in the "blown-blown" technique, which enjoys many advantages, especially in terms of production speed, it is relatively difficult to control the internal profile of the bottle to a high degree of precision, especially to ensure that the walls have a uniform and sufficient thickness. Thus far it has been impossible to use the blown-blown technique to reliably form a bottle whose internal profile must be locally modified for a specific functional need. Thus, for example, in the case of bottles designed for holding liquid substances of medical and/or cosmetic nature it would be very advantageous to be able to locally change the internal profile of the neck, in particular by producing a constriction zone which would control the quantity of product dispensed during application of said substances, especially when using a brush, and a zone which could, for example, also work together with the bottle closure.